Effect of low body temperature during unilateral labyrinthectomy on vestibular compensation in the guinea pig.

Objectives: Vestibular compensation, the recovery that follows unilateral vestibular deafferentation (UVD), is a model for central nervous system plasticity. Recovery from the static symptoms of UVD may involve temperature-dependent processes that modulate the immediate effects of UVD and/or the capability of the central nervous system to undergo adaptive plasticity. In this study we investigated changes in oculomotor and postural vestibular symptoms resulting from low body temperature during UVD.

Material And Methods: To study the effect of low temperatures at the time of UVD on vestibular compensation, we compared the rate of compensation and peak values for postural [roll head tilt (RHT) and yaw head tilt (YHT)] and oculomotor [spontaneous nystagmus (SN)] symptoms in three groups of guinea pigs. Animals in Group 1 (n = 6) were maintained at 38 degrees C throughout unilateral labyrinthectomy (UL). Animals in Group 2 (n = 6) were not temperature-controlled and animals in Group 3 (n = 4) were cooled with ice to 25 degrees C throughout UL.

Results: Cooled animals showed significantly higher rates of SN upon recovery from anaesthesia and took a significantly longer time to compensate. Cooled animals were also slower to compensate for postural symptoms (RHT and YHT), with 2 animals showing no compensation for RHT 52 h after UL.

Conclusion: Hypothermia (25 degrees C) during UVD surgery exacerbates postural and oculomotor symptoms following UL and significantly slows recovery.